The present invention relates to a micro electro mechanical system (MEMS); and, more particularly, to a micro pump used in micro fluid transportation and control, and a method for fabricating the same.
Recently, in fluidics, diagnosis and new medicine development, many studies have been vigorously studied to implement micro pumps on a chip by miniaturizing chemical reaction and diagnosis apparatuses. The micro pumps are driven by electromagnetic force and piezoelectric force, which are caused by thin membranes and valves within a sealed space, or by the movement of solution in a reservoir based on an increased internal pressure, which is caused by an instant heating.
Typically, micro pumps use a sealed space in their structures. In order to form the micro pump, two or three silicon or glass substrates have been employed and fine pattern processing and substrate attaching techniques have been used. That is, for a pump structure, a flow direction and a reservoir are formed on one substrate in a predetermined depth and a pattern, and membrane to form a driving material and electrodes or driving material for supplying driving energy are formed on the other substrate, and then two substrates are combined each other to form a sealed space structure through a pattern alignment of the two substrates
In the above-mentioned conventional micro pump, since an inlet and an outlet are formed in perpendicular to the combined substrate, the micro pump is separately used and it is very difficult to simultaneously implement additional electronic circuits and micro devices due to the combination of the two or more substrates.
Further, the micro pump based on the above structure makes it difficult to implement an integrated micro electro mechanical system (hereinafter, referred to as a MEMS) in which the fluid transportation and analyzing works are simultaneously carried out on a chip such as a concept of lab on a chip (LOC).
Accordingly, it is required that a micro pump be made by silicon surface processing techniques which makes it possible to integrate semiconductor devices on the same chip.
It is, therefore, an object of the present invention to provide a thermally driven micro pump by using general semiconductor processing techniques, such as a trench etching process and an oxidation process of a silicon substrate and a method for fabricating the same.
It is another object of the present invention to provide a thermally driven micro pump which has a planarization structure buried in a silicon substrate and a method for fabricating the same.
In accordance with an aspect of the present invention, there is provided a micro pump comprising: trenches formed in a silicon substrate in order to form a pumping region including a main pumping region and an auxiliary pumping region; first channels formed on both sides of the pumping region; a flow prevention region having the partition layers to resist a flow of fluid such that the flow of the fluid is directed to a predetermined direction, wherein the flow resistance partition layers are disposed in the main pumping region and the first channel adjacent to the main pumping region and wherein the flow resistance partition layers is formed by the silicon substrate in which the trenches are formed; inlet/outlet regions formed at each of the first channels which are disposed on both ends of the pumping region; an outer layer covering the trenches of the silicon substrate and opening portions of the inlet/outlet regions; and a thermal conducting layer formed on the outer layer and over the main pumping region so that a pressure of the fluid in the main pumping region is increased by the thermal conducting layer.
In accordance with an aspect of the present invention, there is provided a method for forming a micro pump comprising the steps of: a) forming trenches in a silicon substrate by etching the silicon substrate and forming first and second groups of silicon lines, wherein the silicon lines in the first group have a different aspect ratio from those in the second group and wherein the etched silicon substrate is divided into first and second regions; b) thermally oxidizing the first and second regions so that the first region is fully filled with a thermal oxide layer and line spaces between the silicon lines in the second region are decreased by a thermal oxide layer; c) covering the silicon substrate, in which the trenches are formed, with a polysilicon layer; d) forming inlet/outlet regions by patterning the polysilicon layer and opening the first and second regions; e) removing the thermal oxide layers in the first and second regions, thereby forming a pumping region of the micro pump, where in the pumping region has main and auxiliary pumping regions and wherein the main pumping region includes the first and second silicon lines; and f) forming a thermal conducting layer on the polysilicon layer.